Polyvinyl alcohol fibers of improved dyeability



Fell 1962 KENICH] TANABE ET AL 3,023,182

POLYVINYLIALCOHOL FIBERS OF IMPROVED DYEABILITY Filed Jan. 19, 1959 POLYVI NYL. ALCOHOL.

WATER- SULFO- GROUP POLYMER LSPINNING SOLUTION 'SPINNING STRETCHING HEAT TREATMENT ACETALIZATION PRODUCT INVENTOR S KENICHI I TANABE YASUJI OHNO gro'ups.

itcti ltaes mm 3,923,1d2 Patented Feb. 27, 19%2 tiic This invention relates to polyvinyl alcohol fibers having improved dyeability. y

It is well-known that fibers of hydroxylated', polymers such aspolyvinyl alcohol orhydrolyzed copolymers of vinyl esters with minor amounts of polyme'rizable vinyl or vinylidene compounds can be obtained by dry or' wet spinning from aqueous solutions thereof. However, such fibers show undesirable sensitivity to water, especially in hot water. T The fibers generally shrink more than 10% of their length in water at room temperatures, and dissolve in hot water at 70-90 C.

In order to improve the properties of the fibers, the spun fibers are usually subjected to a heat treatment at temperatures in the range of 200250 C. followed by acetalization with formaldehyde. By heat treatment the wet softening temperature of the fibers, that is the temperature at which the fibers shrink 10% of their length when immersed for 30 minutes in water, can be raised to 60-110 C. If after heat treatment the fibers are further reacted with formaldehyde the wet softening temperature can be raised to 100-130 C. and the fibers do not dissolve in 150 C. water. Fibers so treated have sufiicient wet heat resistance for practical uses.

A disadvantage of polyvinyl alcohol fibers treated as above indicated is that these fibers have poor dyeability. Untreated polyvinyl alcohol fibers may have dyeability similar'to cellulose fibers with direct colors due to the presence of hydroxyl groups, but heat treatment adversely afiects dyeability with direct colors such that after heat treatment the dyeability is ahnost the same or poorer than that of cotton fibers. By acetalization after heat treatment, the dyeability with direct colors usually decreases further as a result of the reaction of accessible hydroxyl Dye absorption of heat treated and acetalized polyvinyl alcohol fibers with respect to direct colors is usually about 3080% that of cotton.

Polyvinyl alcohol fibers which are acetalized in aqueous solution directly after being spun without intermediate heat treatment, have good afiinity for direct dyes. This is .believed due to the increase in accessible hydroxyl groups resulting from swelling of the fibers during acetalization, which increase more than oflsets blocking of hydroxyl groups as a result of acetalization. However, the wet softening temperature of the fibers is usually below about 60 C. and the fibers shrink considerably in boiling Water and become gelatinous and sticky. If the degree of acetalization is increased, the atfinity for direct dyes decreases greatly while the resistance to shrinkage in boiling water is still poor.

It is an object of this invention to provide polyvinyl alcohol fibers having improved dyeability.

Other objects of the invention will be apparent from the following specification and claims.

In accordance with the present invention, polyvinyl ali cohol fibers having improved dyeability are prepared from a polyvinyl alcohol spinning solution having incorporated therein a water-soluble, sulfo-group containing polymeric material. The said spinning solution is spun into fibers in accordance with wet or dry spinning techniques to form the improved fibers of the invention. The fibers are prefwith a sulfo-group containing aldehyde or acetal thereof.

Other sulio-group containing polymers can also be used in the invention as will be more fully described hereinafter.

In a preferred practice of the invention, polyvinyl alcohol containing at least 70'mol percent vinyl alcohol is'acetalized by reaction with a sulfo-group containing aldehyde or acetal. Specific examples of suitable sulfo-containing aldehydes include aliphatic aldehydes such as sulfoacetaldehyde (formyl methane sulfonic acid), disulfoacetaldehyde, a-sulfopropionaldehyde, B-sulfopropionaldehyde, B-sulfobutyraldehyde, 'y-sulfobuytraldehyde, a,a-dimethy1- -fi-sulfopropionaldehyde, 'y-sulfovaleraldehyde, w-sulfononylaldehyde, and the like, as well as aromatic aldehydes such as ortho-, meta-, and par-a-sulfobenzaldehyde, 2,4-disulfobenzaldehyde, 3,5-disulfobenzaldehyde, sulfonapm thaldehyde, and the like. Acetals of the above aldehydes including methyl, ethyl, propyl, butyl, and the like can be employed. I

The sulfo aldehydes or acetals are reacted with the polyvinyl alcohol in the presence of a mineral acid catalyst. Examples of suitable catalysts include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, and the like. It is generally preferable to carry out the reaction in aqueous solution. Other solvents such as alcohols can be employed. The acetalization can be carried out by dispersing powdered polymer in an aqueous salt solution containing mineral acid and the suite-aldehyde or acetal. Usually acetalization temperatures in the range of 40-90 C. and acetalization times of 1-60 hours are suitable although temperatures and times outside these ranges can be used. The polyvinyl alcohol polymer to be sulfoacetalized should contain at least 70 mol percent vinyl alcohol units. The polymer may comprise partially saponified polyvinyl acetate, or polyvinyl alcohol partially acetalized with a monoaldehyde. The polymer may comprise the saponification product of a copolymer of vinyl acetate with comonomers such as acrylonitrile, vinyl chlobe spun in accordance with the invention to prepare the improved fibers, it is preferred to blend the sulfo-acetalized polymer with a major amount of straight polyvinyl alcohol and spin this blend to form the novel fibers of the invention. Fibers spun from the blend of sulfo-acetalized polyvinyl alcohol and untreated polyvinyl alcohol generally have better mechanical properties and wet heat resistance after further processing steps.

After sulfo-acetalization and prior to spinning the mineral acid is usually neutralized and removed from the acetalized polyvinyl alcohol by dialysis. Alternatively, however, the acid may be neutralized and the resulting salt left in the spinning solution. Fibers produced by wetspinning salt-containing spinning solutions have more circular cross-section.

In addition to the above-described practice of the invention, the invention can also be carried out by spinning polyvinyl alcohol blended with other water soluble sulfogroup containing polymers. Examples of such additional sulfo-polymers include vinyl sulfonic acid polymers and copolymers of vinyl sulfonic acid with'comonomers such as acrylonitrile, vinyl chloride, acrylic acid, methacrylic acid, and the like, said copolymcrs containing at least 5 mol percent vinyl sulfonic acid radicals. Other sulfopolymers which may be used include polymers prepared by acetalizing polyvinyl alcohol with a haloaldehyde or acetal and reacting the resulting polymer with sodium sulfite, sodium acid sulfite, or sodium thiosulfate. Also polymers prepared by reacting allylchloride-containing polymers such as vinyl alcohol-allylchloride copolymers with sodium sulfite, sodium acid sulfite, or sodium thiosulfate can be used. The sulfo-group containing polymers are blended with untreated polyvinyl alcohol to form a homogeneous aqueous spinning solution. The sulfopolymer is used in amount such that fibers formed from the blend contain 0.01l% by weight sulfo-group sulfur. The polymer blend is composed of a major amount of polyvinyl alcohol, preferably about (30-95% by weight polyvinyl alcohol.

Polyvinyl alcohol which is used in the invention is a linear synthetic polymer consisting of at least about 98% vinyl alcohol units, -'-CH --CHOH-. Polyvinyl alcohol having a degree of polymerization greater than 800 and preferably in the range 1000-3000 is employed.

The sulfo-group containing polymeric spinning solution is spun by extruding the aqueous solution through small holes in a spinning jet into a medium effective to remove water therefrom. In wet spinning processes said medium is usually a concentrated aqueous solution of a coagulating salt such as sodium sulfate or ammonium sulfate while in dry spinning techniques air or an inert gas such as nitrogen is employed. Suitable spinning conditions for preparing the sulfo-group containing fibers of this invention are described, for example, in 11.5. Patent 2,642,333 and in Tomonari et a1. application Serial No. 336,166 filed February 10, 1953, now Patent No. 2,988,802.

The fibers are preferably stretched to a draw ratio of about 2:1 to 12:1 during or after spinning. For wet spun filaments, the stretching can be carried out directly after spinning while the fibers are Wet at room temperature up to 100 C. to a draw ratio of about 5:1. For stretching to higher draw ratios, it is preferred to conduct the stretching in a heated medium such as air at 100-250 C.

The oriented fibers are heat treated to improve the wet heat resistance thereof. The heat treatment is usually carried out by heating the fibers in a medium such as air at 210-250 C. for 2 seconds to 5 minutes.

Subsequently, the fibers containing 0.01 to by weight sulfa-group sulfur can be acetalized by reaction with a monoor dialdehyde having up to about 20 carbon atoms until about 5-50% of the vinyl alcohol groups have been acetalized. The acetalization is conveniently carried out in an aqueous solution containing 02-10% aldehyde, 520% sulfuric acid and 0-25% sodium sulfate or ammonium sulfate at temperatures of 40-80 C. for times ranging from a few minutes, e.g. 10 minutes, to several hours, e.g.' 5 hours. Examples of suitable monoand dialdehydes which can be used are formaldehyde, benzaldehyde, glyoxal, propionaldehyde, butyraldehyde, valeraldehyde, and the like.

Practice of the present invention results in the produc tion of fibers which have good dyeability for direct and basic dyestuffs. The fibers are substantially transparent and have substantially uniform cross section. Additionally, the fibers have ion-exchange properties and are thus useful as ion-exchangers.

The fiber of the invention can be pretreated with polyamines such as polyethyleneamine thereby to increase the aflinity thereof to acid dyestufis.

The following examples illustrate the invention.

Example I An aqueous solution containing by weight 6% polyvinyl alcohol which had a mean degree of polymerization of 1600, 6% sulfuric acid, and 4% of the sodium salt of sulfo'acetaldehyde dimethyl acetal was heated at'70" C.

for 7 hours with agitation. After the reaction, the excess acid was neutralized with caustic soda, and the solution was dialyzed by parchment paper in flowing water for 3 days. The solution was then concentrated to obtain polymer in film form. The polymer had a degree of acetalization of 23.5% and contained by weight 6.38% sulfur.

A spinning solution was formed by dissolving 14.4 g. of the acetalized polyvinyl alcohol and 120.6 g. of straight polyvinyl alcohol in water to form a solution containing 15% by weight polymer. The solution was wet spun to form fibers. The fibers were heat treated and subsequently treated in an aqueous solution containing by weight 5% formaldehyde, 15% sulfuric acid and 15% sodium sulfate at 70 C. for 1 hour. The resulting fibers contained 0.61% sulfur. The fibers were transparent and had a uniform cross section upon microscopic examination.

The fibers had 10 mg./ g. dyeing affinity and dyed beautifully when dyed in a bath containing by weight of the fibers 2% direct dyestutf Nippon Fast Violet BB. By

way of comparison, a polyvinyl alcohol fiber prepared similarly but containing no sulfur had 2.0 mg./ g. dyeing affinity. The fibers of the invention were dyed with basic dyestuffs such as Rhodamine B andBismark brown and showed clear color tone. Where the fibers are first dipped in an aqueous solution of polyethylenepolyamine having a low degree of polymerization and dyed, they had good dyeability for direct and acid dyestuffs. The dyeability of straight polyvinyl alcohol fibers where treated similarly with polyethylenepolyamine was not substantially improved.

Example II An aqueous solution containing g. of the same polyvinyl alcohol used in Example I, 84 g. of fl-sulfopropionaldehyde dimethylacetal, and 1676 g. of water was heated at 70 C. for 26 hours. The solution was treated as described in Example I to obtain a polymer film. The polymer so obtained had a 25.6% degree of acetalization and contained 6.57% sulfur.

12.2 g. of the acetalized polyvinyl alcohol and 37.8 g. of straight polyvinyl alcohol were dissolved in water to form a 15% polymer spinning solution. The solution was Wet-spun to form fibers which contained 1.60% sulfur. After heat treatment, the fibers were acetalized in an aqueous bath containing by weight 5% formaldehyde, 12% sulfuric acid, and 15% sodium sulfate at 70 C. for 1 hour.

The fibers were nearly transparent and had uniform cross-section. The fibers dyed beautifully with direct dyestuffs and showed improved dyeing affinity to basic dyestuffs similarly as shown in Example 1.

Example 111 An aqueous solution consisting of 2.4 kg. of polyvinyl alcohol having a mean degree of polymerization of about 1500, 2 kg. sulfuric acid, 5.6 kg. of 28.5% aqueous solution of fi-sulfobutyraldehyde and 30 kg. of water was heated to 60 C. for 30 hours. The acetalized polyvinyl alcohol had a degree of acetalization of 21.0% and contained 5.84% sulfur. After the acetalization, the acid in the solution was exactly neutralized by the addition of a 10% solution of caustic soda without dialysis. To the resulting solution was added 35 kg. of straight polyvinyl alcohol, and water was added to adjust the polymer concentration to 15% by weight.

The solution was wet-spun and the resulting fibers were heat treated and then acetalized at 60 C. for one-half hour in an aqueous bath containing by weight 0.2% terephthaldehyde, 2% sulfuric acid and 10% sodium sulfate. The resulting fiber contained 0.355% sulfur by weight and had a uniform, almost circular cross-section. The 'fiber could be dyed beautifully as the fiber in Example II.

aoaarea About 100 g. of a polymer comprised of 94 mol percent vinyl alcohol and 6 mol percent allylchloride was admixed with 400 g. of an aqueous solution containing 15% sodium sulfite and the mixture was heated for 24 hours. After reaction, the mixture was dialyzed in flowing water by cellophane to remove unreacted substances. The solution was then concentrated to recover the polymer. The polymer contained 0.8% sulfur- The polymer obtained as above described in amount of 54 g. was mixed with 96 g. of polyvinyl alcohol having 1600 degree of polymerization and the mixture diluted with water to form a 15% polymer spinning solution. The solution was wet spun to produce fibers containing 0.29% by weight sulfur. These fibers had good dyeability after heat treatment and acetalization.

Example V About 20 g. of sodium polyvinyl sulfonate having about 500 degree of polymerization was admixed with 130 g. of polyvinyl alcohol and the mixture Was diluted with water to about 16% by weight polymer. This solution was wet spun by extrusion into substantially saturated sodium sulfate solution. The resulting fibers contained 3.25% sulfur. ized. The thusly obtained fibers had considerably more uniform cross section than straight polyvinyl alcohol fibers, and had good dyeability to direct dyestuffs.

Example VI To an aqueous solution containing about 20% by weight sodium sulfite was added B-chloropropionaldehyde, and the mixture was heated to obtain a water-soluble polymer containing sulfo-groups, the formula of which was not definitely known. The polymer was dialyzed in flowing water by parchment paper and the solution was concentrated to recover a hygroscopic polymer, which polymer contained 8.10% sulfur.

About 120 g. of the polymer and 480 g. of 1600 degree of polymerization polyvinyl alcohol were dissolved in water to form a 16% by weight of polymer solution. The solution was wet spun and the resulting fibers were heat-treated and formalized. Transparent fibers containing 1.62% sulfur and having good dyeability to direct and basic dyestufis were obtained.

Example VII The sulfoacetalized polyvinyl alcohol of Example I in amount of 22 g. and 378 g. of straight polyvinyl alcohol were dissolved in water to obtain an aqueous solution containing 30% polymer. The solution was dry spun to form fibers containing 0.34% by weight sulfur. After heat treatment and formalization, the fibers had good dyeability to direct and basic dyestuffs.

Example VIII An aqueous solution containing by weight 6% of a copolymer of vinyl alcohol and vinyl chloride having a mean degree of polymerization of about 800, the copolymer containing 85.3 mol percent vinyl alcohol and 14.7 mol percent vinyl chloride, 5% sulfuric acid, and 4.3% of the sodium salt of B-sulfobenzaldehyde was heated at 60 C. for 6 hours with agitation. After reaction, the

The fibers were heat-treated and formalsolution was neutralized with caustic soda and dialyzed in flowing water for 3 days. The solution was concentrated to recover polymer. The polymer contained 6.03% sulfur by weight.

About g. of the above polymer and 110 g. of untreated polyvinyl alcohol were dissolved in water to obtain a by weight polymer solution. This solution was wet spun and the resulting fibers heat-treated and formalized to obtain product fibers having 0.45% by weight sulfur which had good dyeability similar to those of the preceding examples.

We claim:

1. A spinning solution effective to produce fibers of desirable characteristics particularly with respect to dyeability which comprises water containing dissolved therein I polyvinyl alcohol and a water-soluble sulfo-group containing vinyl polymer, the amount of sulfo-group sulfur being 0.01 to 10% of the total polymer weight.

2. A spinning solution effective to produce fibers of desirable characteristics particularly with respect to dyeability which comprises polyvinyl alcohol and a watersoluble sulfo-acetalized polyvinyl alcohol, the amount of sulfa-group sulfur being 0.01 to 10% of the total polymer weight.

3. A spinning solution effective to produce fibers of desirablecharacteristics particularly with'respect to dyeability which comprises polyvinyl alcohol and a watersoluble sulfa-acetalized polyvinyl alcohol, the-amount of sulr'o-group sulfur being 0.01 to 10% of the total polymer weight, 5 to 50% of the vinyl alcohol units in the combined polymers being acetalized by reaction with an aldehyde having up to 20 carbon atoms.

4. A polyvinyl alcohol fiber consisting of a polymer blend of polyvinyl alcohol and a water-soluble sulfo group containing vinyl polymer, the amount of sulfogroup sulfur being 0.01 to 10% of the total fiber weight.

5. A polyvinyl alcohol fiber consisting of a polymer blend of polyvinyl alcohol and water-soluble sulfoacetalized polyvinyl alcohol, the amount of sulfo-group sulfur being 0.01 to 10% of the total fiber weight.

6. A polyvinyl alcohol fiber consisting of a polymer blend of polyvinyl alcohol and water-soluble sulfoacetalized polyvinyl alcohol, the amount of sul fo-group sulfur being 0.01 to 10% based on the weight of polyvinyl alcohol and sulfa-acetalized polyvinyl alcohol, 5 to 50% of the vinyl alcohol units in the said polymer blend being acetalized by reaction with an aldehyde having up to 20 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS 2,145,345 Dreyfus Ian. 31, 1939 2,300,589 Nelles Nov. 3, 1942 2,642,333 Tornonari June 16, 1933 2,749,208 Cline June 5, 1956 2,822,385 Estes Feb. 4, 1958 2,890,927 Suyama June 16, 1959 2,895,786 Schlack July 21, 1959 OTHER REFERENCES Carpenter, G. B., Wheeler, 0. L.: Textile Research Journal, April 1956, pp. 317-322. 

1. A SPINNING SOLUTION EFFECTIVE TO PRODUCE FIBERS OF DESIRABLE CHARACTERICS PARTICULARLY WITH RESPECT TO DYEABILITY WHICH COMPRISES WATER CONTAINING DISSOLVED THEREIN POLYVINYL ALCOHOL AND A WATER-SOLUBLE SULFO-GROUP CONTAINING VINYL POLYMER, THE AMOUNT OF SULFO-GROUP SULFUR BEING 0.01 TO 10% OF THE TOTAL POLYMER WEIGHT. 